The invention relates to a pattern matching method and a computer program for executing the pattern matching, and in particular, relates to a method suitable to execute pattern matching of a sample containing a periodic structure, and the program.
For example, in a scanning electron microscope (SEM) or the like, which measures and inspects a semiconductor wafer, position checking of a field of view (FOV) or a scanning position to a desired measurement position is carried out, by using pattern matching technique. JP-A-2001-243906 (corresponding U.S. Pat. No. 6,627,888) explains an example of such a pattern matching method.
A pattern matching is carried out by measurement of coincidence between a pattern image, which is called a template and registered in advance, and an image obtained actually by SEM or the like. JP-A-2002-328015 (corresponding USP: US2003/0173516) explains an example of forming a template for pattern matching, based on the design data of a semiconductor element or the like. Formation of the template based on the design data has an advantage in that bothering to obtain an SEM image or the like can be eliminated.
A general pattern matching method, in an image, selects a position with the highest coincidence with a template as a position for movement of a field of view or a measurement object. However, in the case of a pattern where a plurality of equivalent shapes is periodically arranged, pattern selection based on coincidence may unnecessarily largely move a field of view. In the case of a periodic structure, because the same patterns are arranged, average evaluation of these patterns may be allowed by selecting any pattern, in the case where the evaluation is carried out by extraction of one pattern. However, selection of a pattern based on coincidence results in selection of a pattern with the highest coincidence, therefore, there is a possibility for a pattern at a position far from the center of a field of view before pattern matching to be selected.
It is considered to move a field of view by movement of a stage where a sample is arranged, or by deflecting electron beams of SEM so as to move a field of view of SEM, however, unnecessarily large movement of a field of view may increase error components included in a stage or a deflector or the like, and cause erroneous movement of a field of view. Pattern matching methods explained in Patent Documents 1 and 2 are not directed to solve these problems.